Hydrogen, which generates water when burnt, is not a greenhouse gas emitter unlike fossil fuels. Hydrogen thus regarded as a source of clean energy is desirably used in more diverse applications. On the other hand, hydrogen is difficult to liquefy kind easy to react with metals. Further, hydrogen is likely to initiate explosive reactions when muted with oxygen. These properties of hydrogen are associated with difficulties in storage and transportation. These drawbacks of hydrogen are raising the need for a technology that advantageously allows for storage of substances high in hydrogen content as hydrogen carriers, and extraction of hydrogen from the carries right before being used as an energy source.
Examples of the known hydrogen carriers are ammonia and hydrocarbon-based fuels. The patent document 1 describes a technology, wherein hydrogen is produced from ammonia at 400° C. or higher temperatures by using a decomposer and a noble metal catalyst such as Pt, Rh, Pd, or Ru. The patent document 2 describes a technology, wherein hydrogen is produced from ammonia gas decomposed at temperatures between 800° C. and 900° C. by using a nickel/alumina catalyst. The patent document 3 describes a technology, wherein hydrogen is produced from ammonia decomposed at temperatures between 540° C. and 630° C. by using a catalyst containing an aluminum-cobalt oxide.
In the methods conventionally employed to produce ammonia-derived hydrogen, ammonia is reacted at 400° C. or higher temperatures by using various catalysts. These methods, however, necessitate the use of expensive catalysts and high-temperature heat sources, requiring large cost to produce hydrogen. Another problem with these methods is ammonia residue. Due to such problems of the conventional methods, an advantageous technology has been sought to produce hydrogen more efficiently with lower cost in a stable manner.